Excimer laser equipment

Abstract

The present invention relates to excimer laser equipment which is one kind of gas laser, and in particular to a rare gas-halide excimer laser using rare gases and halogens as laser media, and adapted to control the concentration of halogens contained in laser media therewithin on the basis of the result of the measurement of the concentration of halogens in the laser media which is being used for the oscillation of laser rays therein, whereby the stabilized oscillation of the laser is always possible.

What is claimed is: 
     
       1. In an excimer laser which uses a mixture of a rare gas, halogen gas and a buffer gas as a lasing medium, the mixture including respective concentrations of each of the rare, halogen and buffer gases, an apparatus for controlling the concentration of the halogen gas in the mixture, comprising: means for measuring the concentration of the halogen gas in the mixture used as the lasing medium, wherein the measuring means generates a signal corresponding to the halogen concentration;   means for regenerating the mixture used as the lasing medium; and   means for controlling the regenerating means in accordance with the signal from the measuring means.   
     
     
       2. The apparatus of claim 1, wherein the means for measuring the concentration of the halogen gas in the mixture used as the lasing medium comprises: a resistance bridge circuit comprising at least one heat sensitive resistor disposed in a standard gas cell and at least one heat sensitive resistor disposed in a measuring gas cell;   means for detecting an imbalance in the resistance bridge circuit;   a first piping connected to the excimer laser for introducing a first portion of the mixture into the measuring gas cell; and   a second piping for introducing a second gas mixture containing no halogen gas into the standard gas cell.   
     
     
       3. The apparatus of claim 2, wherein the second gas mixture includes concentrations of the rare gas and the buffer gas which are substantially equal to the respective concentrations of the mixture used as the lasing medium in the excimer laser. 
     
     
       4. The apparatus of claim 2, wherein the means for measuring the concentration of the halogen gas in the mixture used as the lasing medium further comprises a material for removing halogens, and wherein the second gas mixture is a second portion of the mixture in the excimer laser, the second portion having passed through the removing material. 
     
     
       5. The apparatus of claim 4, wherein the removing material is a solid substance which forms fixed halogenides. 
     
     
       6. The apparatus of claim 2, wherein the second gas mixture is a second portion of the mixture used as the lasing medium in the excimer laser, the second portion having passed through a cooling trap. 
     
     
       7. The apparatus of claim 1, wherein the means for measuring the concentration of the halogen gas in the mixture used as the lasing medium includes: means for emitting light;   a measuring gas cell for confining a first portion of the mixture used as the lasing medium in the excimer laser;   a standard gas cell for confining a second gas mixture, the second mixture having concentrations of the rare and buffer gases which are substantially equal to the respective concentrations of the mixture used as the lasing medium;   means for directing the light through the measuring gas cell and the standard gas cell; and   means for comparing a first intensity of light transmitted by the measuring gas cell and a second intensity of light transmitted by the standard gas cell.   
     
     
       8. The apparatus of claim 1, wherein the means for regenerating the mixture used as the lasing medium replaces a part or all of the mixture in the excimer laser with fresh mixture. 
     
     
       9. The apparatus of claim 8, wherein the means for controlling the regenerating means turns the regenerating means ON or OFF. 
     
     
       10. The apparatus of claim 1, wherein the means for regenerating the mixture used as the lasing medium adds a suitable quantity of the halogen gas to the mixture used as the lasing medium in the excimer laser. 
     
     
       11. The apparatus of claim 10, wherein the means for controlling the regenerating means turns the regenerating means ON and OFF. 
     
     
       12. The apparatus of claim 1, wherein the means for regenerating the mixture used as the lasing medium adds suitable quantities of the halogen and rare gases to the mixture in the excimer laser. 
     
     
       13. The apparatus of claim 12, wherein the means for controlling the regenerating means turns the regenerating means ON or OFF.